Background and Summary of the Invention
[0001] The present invention relates generally to a scroll-type machine and more specifically
to a scroll-type machine specifically adapted for use in either cryogenic applications
utilizing helium as the refrigerant or as an air compressor.
[0002] The use of helium as a refrigerant is common in very low temperature applications.
However, the cyclic compression of helium presents very unique problems with respect
to compressor design because of the high temperatures encountered during the compression
process; typically more than twice the temperature rise encountered with the use of
more conventional refrigerants. In order to prevent possible damage to the compressor
from these high temperatures, it is necessary to provide increased cooling thereto
such as by circulating large quantities of oil through the compressor.
[0003] Compression of air also results in substantial temperature increases and in addition
thereto presents problems of contamination because the air compression system is an
open system as opposed to the closed systems generally used in refrigeration applications.
Because an air compressor is drawing its suction gas from the atmosphere, various
particulate matter as well as potentially corrosive vapor and gaseous contaminants
may be cycled through the compressor. Accordingly, in these types of compressors,
it is also desirable to circulate substantial quantities of lubricant through the
compressor as well.
[0004] The present invention comprises a scroll compressor, which is specifically adapted
for use in the compression of both helium and air which in addition to the conventional
low pressure oil sump, also includes a second high pressure oil sump in the discharge
chamber. The oil from the low pressure oil sump is circulated to the bearings and
other moving parts in a manner similar to that of conventional scroll compressors.
However, oil from the high pressure oil sump is directed through an external heat
exchanger for cooling and then injected into the compression pockets to aid in cooling
of the compressor as well as to assist in sealing of the wraps and lubricating same.
An oil separator is provided in the discharge chamber of the compressor to remove
at least a portion of the injected oil from the compressed gas to thereby replenish
the high pressure oil sump. A unique level control arrangement is also provided to
prevent excess accumulation of oil in the high pressure oil sump. Relatively large
volumes of oil must be circulated in this manner to prevent overheating of the compressor
during operation as well as to aid in lubrication thereof. It should be noted that
in such cryogenic applications it is exceedingly important that the refrigerant (i.e.
helium) be virtually oil free and hence it is common for such systems to employ multiple
external oil separators to ensure complete removal of the oil injected during the
compression process. This is also true in many applications in which compressed air
is utilized.
[0005] Additional advantages and features of the present invention will become apparent
from the subsequent description and the appended claims taken in conjunction with
the accompanying drawings.
Brief Description of the Drawings
[0006]
Figure 1 is a section view of a hermetic scroll-type compressor in accordance with
the present invention, the section being taken along an axially extending radial plane;
Figure 2 is a fragmentary section view of the compressor of Figure 1 showing the oil
return and injection arrangement;
Figure 3 is a section view of the main bearing housing of the compressor shown in
Figure I, the section being taken along line 3-3 thereof;
Figure 4 is a perspective view of the discharge baffle incorporated in the compressor
of Figure 1;
Figure 5 is a section view of the non-orbiting scroll member forming a part of the
compressor of Figure 1, the section being taken along line 5-5 of Figure 2;
Figure 6 is a schematic view illustrating the refrigeration circuit incorporating
the compressor of Figure 1;
Figure 7 is a section view similar to that of Figure 2 but showing a hermetic scroll-type
compressor specifically adapted for use as an air compressor all in accordance with
the present invention;
Figure 8 is an enlarged fragmentary view of the removable oil return fitting incorporated
in the compressor of Figure 7; and
Figure 9 is a schematic view similar to that of Figure 6 but showing a fluid circuit
incorporating the air compressor of Figure 7.
Description of the Preferred Embodiments
[0007] Referring now to the drawings and more specifically to Figure 1, there is shown a
hermetic compressor of the scroll-type indicated generally at 10 in accordance with
the present invention. Compressor 10 includes an outer shell 12 within which is disposed
a compressor assembly including an orbiting scroll member 14 having an end plate 16
from which a spiral wrap 18 extends, a non-orbiting scroll member 20 having an end
plate 22 from which a spiral wrap 24 extends and a main bearing housing 26 supportingly
secured to outer shell 12. Main bearing housing 26 supports orbiting scroll member
14 and non-orbiting scroll member 20 is axially movably secured thereto with respective
wraps 18 and 24 positioned in meshing engagement such that as orbiting scroll member
14 orbits, the wraps will define moving fluid pockets that decrease in size as they
move toward the center of the scroll members.
[0008] A driving motor 28 is also provided in the lower portion of shell 12 including a
stator 30 supported by shell 12 and a rotor 32 secured to and drivingly connected
to drive shaft 34. Drive shaft 34 is drivingly connected to orbiting scroll member
14 via eccentric pin 36 and drive bushing 38 and is rotatably supported by upper bearing
housing 26 and a lower bearing housing 40 which is also secured to shell 12. The lower
end of drive shaft 34 extends into an oil sump 42 provided in the bottom of shell
12. A reverse rotation prevention and lower counterweight shield assembly 44 is also
supported on drive shaft 34 between lower bearing 40 and motor assembly 28 and serves
to restrict reverse rotation of the compressor on shut down as well as to restrict
flow of oil to the area around the lower end of the rotor. In order to prevent orbiting
scroll member 14 from rotating relative to non-orbiting scroll member 20, an Oldham
coupling 45 is provided being supported on main bearing housing 26 and interconnecting
with both orbiting scroll member 14 and non-orbiting scroll member 20.
[0009] In order to supply lubricant from oil sump 42 to the bearings and thrust surfaces,
an oil pump is provided in the lower end of drive shaft 34 which serves to direct
oil axially upwardly through an eccentric axially extending passage 43 in drive shaft
34. Radial passages may be provided to supply lubricant to the main bearing and/or
lower bearing and a portion of the oil will be discharged from the top of eccentric
pin 36 to lubricate the interface with drive bushing 38 and the interface between
drive bushing 38 and orbiting scroll member 14.
[0010] A partition or muffler plate 46 is also provided extending across the interior of
shell 12 and is sealingly secured thereto around its periphery. Muffler plate 46 serves
to divide the interior of shell 12 into a lower suction chamber 48 and an upper discharge
chamber 50.
[0011] In operation, suction gas will be drawn into suction chamber 48 of compressor 10
through suction inlet 52 and into the moving fluid pockets defined by scroll wraps
18 and 24 and end plates 16 and 22. As orbiting scroll member 14 orbits with respect
to non-orbiting scroll member 20, the fluid pockets will move inwardly decreasing
in size and thereby compressing the fluid. The compressed fluid will be discharged
into discharge chamber 50 through discharge port 54 and passage 56 provided in non-orbiting
scroll member 20 and discharge fitting assembly 58 secured to muffler plate 46. The
compressed fluid then exits compressor 10 through discharge outlet 59. In order to
maintain axially movable non-orbiting scroll member 20 in axial sealing engagement
with orbiting scroll member 14, a pressure biasing chamber 60 is provided in the upper
surface of non-orbiting scroll member 20. A floating seal 62 is positioned within
chamber 60 and cooperates with muffler plate 46 to prevent leakage of discharge gas
flowing into discharge chamber 50 from discharge port 54. Biasing chamber 60 is pressurized
by fluid at intermediate pressure supplied from the fluid pockets under compression
via passages (not shown) in non-orbiting scroll 20.
[0012] With the exception of discharge fitting 58, compressor 10 as thus far described is
similar to and incorporates features described in greater detail in assignee's patents
numbers 4,877,382; 5,156,539; 5,102,316; 5,320,506; and 5,320,507 the disclosures
of which are hereby incorporated by reference.
[0013] As noted above, compressor 10 is specifically adapted for use with helium as a refrigerant.
Because of the nature of helium, the compression of same in a refrigeration compressor
results in the generation of significantly higher temperatures. In order to prevent
these temperatures from becoming excessive, it is necessary to circulate substantially
greater quantities of oil to the various components than typically is necessary when
other more common refrigerants are utilized and to supply oil to the compression chambers
as well. In addition to the need for the circulation of large quantities of oil, it
is also very important that substantially all oil be removed from the compressed helium
before it is supplied to the refrigeration or cryogenic system.
[0014] In order to accommodate these special requirements for use of helium as a refrigerant,
the compressor of the present intention incorporates a generally radially extending
passage 64 in the end plate of orbiting scroll member 14. Passage 64 at its inner
end opens into the chamber defined by hub 66 provided on orbiting scroll member 14
in which bushing 38 and eccentric pin 36 are disposed. The outer end of passage 64
is plugged and an axially extending passage 68 extends upwardly therefrom and opens
into the flow of suction gas entering the compression pockets of the compressor. Passages
64 and 68 thus serve to direct a portion of the oil being thrown out of the top of
eccentric pin 36 to the suction gas flowing into the compression pockets.
[0015] In addition to the supply of oil to the suction gas entering compressor 10, externally
supplied oil is also injected into the fluid pockets during compression thereof. In
order to accomplish this and as best seen with reference to Figures 2 and 5, end plate
22 of non-orbiting scroll member 20 is provided with a pair of generally chordally
extending passages 70 and 72 the inner ends of which communicate with respective axial
passages 74 and 76 opening into a pair of diametrically opposed fluid pockets which
pockets are undergoing compression and hence at a pressure between suction and discharge.
The outer ends of passages 70 and 72 merge into a single passage 78 which opens outwardly
through a sidewall of the end plate 22 of non-orbiting scroll 20. A fitting 80 is
secured to the sidewall of end plate 22 and defines a passage 82 leading from an oil
inlet fitting 84 secured to outer shell 12 to passage 78. In order to accommodate
axial movement of non-orbiting scroll member 20, fitting 80 is formed in two pieces
with lower portion 86 being slidably telescopically received within the lower end
of upper portion 88. Suitable sealing means such as an O-ring will preferably be provided
between upper and lower portions 86 and 88. A relatively short tubular member 90 serves
to sealingly interconnect oil inlet fitting 84 with lower portion 86 of fitting 80.
[0016] In addition to the above, main bearing housing is provided with a plurality of generally
radially extending passages 92 which serve to direct oil accumulating in recess 94
outwardly to Oldham coupling 45. As best seen with reference to Figure 3, there will
preferably be four such radially extending passages 92 positioned in substantially
90° spaced relationship to each other.
[0017] Discharge fitting 58 includes an upper tubular member 96 having a relatively large
diameter threaded bore 98 opening inwardly from the lower end thereof and a depending
locating flange portion 100 which is received within an opening 102 provided in muffler
plate 46. A threaded flanged retainer 104 is received within bore 98 and serves to
sealingly secure discharge fitting 58 to muffler plate 46 and to define a flowpath
for discharge gas from discharge passage 56 into discharge chamber 50.
[0018] Discharge fitting 58 supports an oil separator plate 106 secured to the upper end
thereof in overlying relationship to outlet openings 108. Oil separator plate 106
extends radially outwardly from fitting 58 and includes a plurality of radially spaced
annular depending flange portions 110 that serve to provide a tortuous flowpath for
the discharge gas and thereby aid in separation of entrained oil.
[0019] Oil separated from the discharge gas by separator plate 106 will accumulate in the
lower portion of discharge chamber 50. In order to recirculate this oil, an oil outlet
fitting 112 is provided being secured to shell 12 so as to open into a lower portion
of discharge chamber 50 which defines an upper oil sump. Oil from outlet fitting 112
is supplied to oil inlet fitting 84 as described in greater detail below.
[0020] In order to prevent excessive accumulation of oil in discharge chamber 50, a lubricant
level oil return assembly 114 is provided which operates to return excessive oil to
lower sump 42 through muffler plate 46. Oil return assembly 114 includes a through
fitting 116 sealingly secured to and extending through muffler plate 46 adjacent an
outer peripheral edge thereof from which a tube 118 extends to discharge fitting 58.
Return fitting 116 defines a passage 128 extending therethrough which opens into the
lower pressure suction chamber 48 via opening 130. If desired, a suitable filter may
be provided within passage 128 to prevent any particles from being returned to the
lower sump. Discharge fitting 58 includes a passage 120 extending axially downward
from the upper end thereof and communicating at its lower end with a radially inwardly
extending passage 122 via a restricted portion 124. The upper end of passage 120 is
sealed off with a suitable plug 123. Tube 118 communicates with axially extending
passage 120 via a second radially extending passage 126 located above radial passage
122.
[0021] As the oil level in discharge chamber rises, oil will flow into passage 122. Should
the oil level rise above the lower edge of restrictor 124, oil will begin to flow
through restrictor 124 into passage 120 and thence to passage 126, tube 118 through
fitting 116 and be returned to the lower sump 42. It should be noted that because
chamber 50 is at a pressure (discharge) greater than that of the pressure in chamber
48, oil will be forced through passage 122, restrictor 124, etc and hence returned
to lower sump 42 so long as the level 127 in discharge chamber 50 remains above the
lower edge of restrictor 124. However, restrictor 124 will operate to limit the flow
of compressed gas into suction chamber 48 during periods in which oil level 127 is
below the lower edge of restrictor 124. It should also be noted that, if desired,
plug 123 could be omitted thereby leaving passage 120 in open communication with the
compressed gas in discharge chamber 50. In such case, it is necessary that restrictor
124 be located downstream of passage 120, i.e., in passage 126, tube 118 or through
fitting 116. It should be noted that passage 120 will preferably be located substantially
coaxial with the axial center of compressor 10. This will ensure that opening of restrictor
124 and/or passage 126 into passage 120 is in close proximity to the center axis 129
of the compressor and will greatly reduce the effect of tilting of compressor 10 on
the level of oil retained in the discharge chamber 50.
[0022] In order to reduce the amount of oil entrained in the discharge gas that is carried
over into discharge outlet 59 and also to resist large quantities of oil being expelled
therethrough should compressor 10 be tilted so as to raise the oil level above the
lower portion of discharge outlet 59, a baffle member 132 is secured to shell 12 in
overlying relationship to the inner end of discharge outlet 59. As shown in Figure
4, baffle member 132 may be in the form of a box having an opening 134 on the top
sidewall thereof and an open end 136 which is sealingly secured to the inner surface
of shell 12. Alternately, baffle member 132 may be cylindrical in shape with one end
closed and opening 134 being oriented so as to face upwardly away from the upper surface
of the lubricant in discharge chamber 50.
[0023] Referring now to Figure 6, compressor 10 is shown incorporated in a refrigeration
or cryogenic circuit specifically designed for use of helium as a refrigerant. As
shown therein, compressed helium flows from compressor 10 via line 138 to a heat exchanger
140 which serves to separate oil therefrom. From heat exchanger 140, the compressed
helium is routed serially through additional oil separators 142 to ensure substantially
complete removal of entrained oil therefrom after which it is directed to a condenser
144 and then to additional system components (not shown) such as an evaporator and
then returned to compressor 10 via line 141. Oil collected in discharge chamber 50
is directed from oil outlet 112 to a heat exchanger 146 via line 148 for cooling.
Oil from heat exchanger 146 together with separated oil from heat exchanger 140 and
oil separators 142 is then supplied to oil inlet fitting 84 via line 143 from which
it is directed to the respective fluid pockets under compression. Because this oil
is at substantially discharge pressure, oil will easily be caused to flow into the
desired fluid pockets under compression which will be at a pressure above suction
pressure but below discharge pressure. As shown, suitable check valves 150 are included
at both discharge outlet 59 and oil outlet 112 to prevent undesired reverse flow of
fluids. Additionally, lubricant separated in heat exchanger 140 as well as lubricant
separators 142 will also be supplied to oil inlet fitting 84 via line 145 for injection
into the moving fluid pockets. It should be noted that it is desirable that the pressure
of the lubricant being returned to oil inlet fitting 84 from the various sources be
at substantially the same pressure. Accordingly, suitably sized restrictors 147 are
provided at the outlets of each of the oil separators 142 and heat exchangers 140
and 146.
[0024] As will now be appreciated, compressor 10 is designed to provide a high volume of
oil flow to the compressor to both lubricate the various portions thereof as well
as to ensure adequate cooling of the compressor. Additionally, compressor 10 includes
an integral oil separator to aid in removal of the oil from the compressed refrigerant
as well as to ensure an adequate supply of oil for injection into the compressor.
Additionally, the provision for oil injection into the suction inlet provides insurance
that the level of oil in the discharge chamber will be maintained whereas the overflow
arrangement prevents this level from becoming excessively high.
[0025] Referring now to Figure 7, a second embodiment of a compressor in accordance with
the subject invention is disclosed which compressor is specifically adapted for use
as an air compressor. Except as noted below, compressor 152 is substantially identical
to compressor 10 including without limitation both the oil injection into the fluid
pockets under compression, the injection of oil into the suction gas flowing to the
compression pockets and the internal oil separator incorporated in compressor 10 as
shown in Figure 1. Accordingly, corresponding portions thereof have been indicated
by the same reference numbers primed.
[0026] In place of the suction inlet 52 incorporated in compressor 10, compressor 152 includes
an inlet assembly 154 which includes conduit 156 secured to the outer shell 12' which
is adapted to receive a threaded connection for suction inlet conduit 158. A suction
filter assembly 160, which may also include a muffler if desired, is secured to the
other end of conduit 158 and serves to filter out particulate matter that could result
in excessive wear as well as to muffle possible noise of the air being drawn into
compressor 152.
[0027] Additionally, discharge fitting 162 of compressor 152 includes a restricted opening
164 at its inner end. Restricted opening 164 serves to restrict the flow of compressed
air out of discharge chamber 50' which is particuiarly important during periods of
compressor operation in which the back pressure loading is at zero or very low as
this build up of discharge pressure in chamber 50' acts together with the intermediate
pressure in biasing chamber 60' to bias the non-orbiting scroll member 20' axially
into sealing engagement with orbiting scroll member 14'. Additionally, in order to
ensure sufficient biasing force on non-orbiting scroll member 20' to begin compressing
air on compressor start up as well as to ensure proper initial sealing between seal
62' and muffler plate 46', a plurality of springs are provided in biasing chamber
60' acting between a lower surface of seal 62' and the bottom surface of biasing chamber
60'.
[0028] It should be noted that the inclusion of restrictor 164 in discharge fitting 162
will not appreciably reduce system efficiency because during normal operation, the
density of the compressed air flowing therethrough will be substantially greater than
at low pressure operation.
[0029] In addition to the above, compressor 152 incorporates a modified arrangement for
preventing accumulation of excessive oil in the discharge chamber. As best seen with
reference to Figures 7 and 8, compressor 152 includes an elongated member 166 extending
axially inwardly through a suitable fitting 168 provided on the top portion of outer
shell 12' and having a lower end 170 threadedly received in a threaded opening 172
provided in muffler plate 46'. In order to prevent leakage through fitting 168 from
discharge chamber 50', elongated member is provided with a shoulder 174 adjacent the
upper end against which a suitable O-ring 176 is seated. Similarly, in order to prevent
leakage through opening 172 in muffler plate 46', a second shoulder 178 is provided
against which O-ring 180 is seated.
[0030] Elongated member 166 comprises an upper member 182 having an axially extending bore
184 provided therein and a plurality of circumferentially spaced radial bores 186
opening into bore 184 adjacent the upper end thereof. A lower member 188 is also provided
having reduced diameter portion 190 provided at the upper end thereof which is sized
to be threadedly received in bore 184 of upper member 182. A central bore 192 extends
axially from the upper end of lower member 188 forming a continuation of bore 184
and terminates adjacent the lower end where a restricted opening 194 is provided opening
outwardly from the bottom of lower member 188. A suitable filter 196 is provided fitted
in the upper end of lower member 188 and serves to filter any debris from oil being
returned to the lower sump. Elongated member 166 is designed for easy removal and
disassembly so as to enable periodic cleaning and/or replacement of filter 196. It
should be noted that the distance from shoulder 178 to passages 186 will determine
the oil level within discharge chamber 50'. Further, when the oil level is below passages
186, the restricted opening 194 will operate to limit the leakage of compressed air
to the suction chamber.
[0031] Compressor 152 also incorporates a pressure relief valve 198 secured to outer shell
12' which is operative to vent discharge chamber 50' to atmosphere in response to
an excessive pressure therein.
[0032] In addition to the above, compressor 152 includes a temperature sensor 228 extending
into the oil sump provided in the lower portion of the discharge chamber 50'. Temperature
sensor 228 is interconnected with the power supply to motor 28' and operates to deenergize
same in response to an excessive temperature in the discharge chamber. It should be
noted that while temperature sensor 228 is positioned so as to be immersed in the
oil and hence will be primarily responsive to excessive oil temperature, it will also
respond to excessive discharge gas temperature in the event the oil level drops below
sensor 228.
[0033] Referring now to Figure 9, a schematic of a compressor air and oil circulation circuit
is shown incorporating compressor 152., Discharge outlet 162 of compressor 152 extends
via line 200 to an oil separator 202 which operates to remove entrained oil from the
compressed air. From oil separator 202, the compressed air is directed to a suitable
storage tank (not shown) via line 204. A blow down valve 206 and associated silencer
208 is provided along line 204 and before a check valve 210 and serves to release
any residual pressure in discharge chamber 50', oil separator 202 and lines 200 and
204 when compressor 152 is shut down. This pressure is vented to ensure that compressor
152 will not be required to start against a heavy pressure load that may exist. Preferably,
blow down valve 206 will be a suitable solenoid actuated valve and check valve 210
will ensure that the tank or reservoir pressure is not vented.
[0034] Oil return outlet 112' is connected to a suitable oil cooler 212 via line 214. A
check valve 216 is provided in line 214 adjacent outlet 112'. In order to prevent
excessive cooling of the oil, a suitable bypass line 218 and associated valve 220
is provided which may operate to direct a portion or all of the oil directly to return
line 222 thereby bypassing heat exchanger 212. Return line 222 extends back to oil
injection inlet fitting 84' provided on compressor 152. Additionally, oil separated
by oil separator 202 is also supplied to oil injection fitting 84' via line 224. In
order to prevent debris entrained within the oil from being injected into the fluid
pockets under compression, filters 226 are provided in both lines 222 and 224.
[0035] While it will be apparent that the preferred embodiments of the invention disclosed
are well calculated to provide the advantages and features above stated, it will be
appreciated that the invention is susceptible to modification, variation and change
without departing from the proper scope or fair meaning of the subjoined claims.
1. A scroll-type compressor comprising:
an enclosed shell (12);
a first scroll member (14) disposed within said shell and including a first end plate
(16) having a first spiral wrap (18) thereon;
a second scroll member (20) disposed within said shell and including a second end
plate (22) having a second spiral wrap (24) thereon;
said scroll members being supported for orbital movement relative to one another;
said first and second spiral wraps (18,24) being intermeshed so as to define moving
fluid pockets which decrease in size in response to said orbital movement to compress
a gas in said shell;
a lubricant sump (42) disposed in said shell;
a suction inlet (52;154) through said shell for supplying suction gas to said scroll-members;
a lubricant delivery system for delivering lubricant from said. sump to said fluid
pockets;
a first lubricant separator (106) disposed within said shell, said lubricant separator
being operative to separate lubricant from said compressed gas and return said separated
lubricant to said sump; and
a second lubricant separator (132) disposed within said shell, said second lubricant
separator being downstream from said first lubricant separator and operative to separate
lubricant from said compressed gas and return said lubricant to said sump.
2. A scroll-type compressor as set forth in claim 1 further comprising a filter (196)
within said shell for filtering said lubricant.
3. A scroll-type compressor as set forth in claim 1 or 2, wherein said lubricant delivery
system further operates to inject lubricant into said suction gas.
4. A scroll-type compressor as set forth in claim 3 further comprising a second lubricant
sump (50;50'), said lubricant injected into said suction gas being supplied from said
second sump to thereby replenish the first mentioned said lubricant sump.
5. A scroll-type compressor as set forth in claim 1 further comprising a temperature
sensor (228) in said lubricant sump, said temperature sensor being operative to de-energize
said compressor in response to an excessive temperature in said lubricant sump.